Heat exchanger for high stage generator of absorption chiller

Abstract

An absorption cooling machine of the type which uses a refrigerant and an absorbent and which includes a high stage generator, absorber, condenser, heat exchangers, and an evaporator and means for connecting the components to one another to form a closed absorption cooling system. The solution side of the high stage generator is fluidically divided into two sections with a partition plate whereby gas exiting one section at relatively high temperature is further cooled in a second section called a flue gas recuperator (FGR) to improve overall burner efficiency.

Description

BACKGROUND OF THE INVENTIONThe invention relates in general to an absorption cooling system and more specifically to an improved heat exchanger for a high stage generator of an absorption chiller.A direct-fired, double effect, absorption chiller / heater consists of an evaporator, absorber, condenser, high and low stage generators, separator, solution heat exchanges, refrigerant / solution pumps, burner and gas train assembly, purge, controls and auxiliaries. Water is used as the refrigerant in vessels maintained under low absolute pressure (vacuum). In the cooling mode, the chiller operates on the principle that under vacuum, water boils at a low temperature, thereby cooling the chilled water circulating through the evaporator tubes. A refrigerant pump is used to circulate the refrigerant water over the evaporator tubes to improve heat transfer.To make the cooling process continuous, the refrigerant vapor must be removed as it is produced. To accomplish this, a lithium bromide solution...

AI Technical Summary

Benefits of technology

According to the present invention, in a standard liquid tube type high stage generator, a partition plate is positioned toward the end of the heat exchanger dividing the high and low pressures of a high and low stage of a triple or double effect absorption chiller cycle. The section from the fire tube up to the partition plate brings down the flue temperature up to approximately 650 F for a triple effect and up to 400 F for a double effect cycle. There is significant amount of energy remaining in the exhaust, which is recovered by preheating or boiling solution at a lower pressure in the remaining section of the flue passage, called flue gas recuperator (FGR). The FGR is a flooded type heat exchanger. Although the liquid tubes of both high stage generator and FGR section are shown to be of the same height, the tubes of FGR may be taller in order to reduce solution charge. The saturated (or heated) solution or solution vapor mixture goes to a conventional lower stage generator where an effect of advanced absorption cycle is materialized by generating more vapor utilizing high pressure steam generated in the high stage generator. The primary object of the invention is to modify a conventional high stage generator of a specific tonnage double effect chiller for a triple effect system. Since a triple effect chiller will have a lower gas firing rate (due to higher COP), there is virtually no change in the flue side flow length; thus the net pressure drop will be lower (due to lower flow rate). The addition of partition plate adds only marginal cost to the generator, making it economical and compact.

Problems solved by technology

As this process continues, the lithium bromide becomes diluted, reducing its absorption capacity.

In the high stage generator a significant amount of energy is lost in the exhaust flue gas.

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